Current Saturation and Steep Switching in Graphene PN Junctions using Angle-dependent Scattering
Graphene’s ultra-high carrier mobility (200,000cm2/Vs on hBN) makes it promising for high speed applications; however the absence of a band-gap makes it hard to design logic elements out of graphene. It is possible to open a bandgap in graphene by applying strain or by confining it in one direction into nanoribbons, but in the process bandstructure gets distorted near Dirac point and the carrier mobility decreases. A recent set of papers have exploited instead the angle dependent transmission across graphene pn junctions (GPNJ). Since the opening angle is gate tunable, a sequence of angled junctions can turn off the electrons using gateable momentum filtering in the absence of a band-gap (instead, the ideas use a transmission gap). In the absence of edge scattering, momentum filtering is predicted to give large ON, low OFF current and a steep subthreshold swing (SS). In this paper, we calculate the transfer (ID-VG) and output (ID-VD) characteristics of a GPNJ switch and show current saturation using gate geometry alone.